diff --git a/e2e/fixtures/index.ts b/e2e/fixtures/index.ts
index 07a6b64..55c8396 100644
--- a/e2e/fixtures/index.ts
+++ b/e2e/fixtures/index.ts
@@ -2,3 +2,4 @@ export { test, expect } from './auth.fixture';
 export { createTestUser, registerUser, loginUser } from './auth.fixture';
 export type { TokenPair } from './auth.fixture';
 export { createTestListing, createListing } from './listings.fixture';
+export { buildVnpayCallbackData, buildMomoCallbackData } from './payments.fixture';
diff --git a/e2e/fixtures/payments.fixture.ts b/e2e/fixtures/payments.fixture.ts
new file mode 100644
index 0000000..b325297
--- /dev/null
+++ b/e2e/fixtures/payments.fixture.ts
@@ -0,0 +1,111 @@
+import * as crypto from 'crypto';
+
+/**
+ * Generates a valid VNPay callback payload with a correct HMAC-SHA512 signature.
+ *
+ * Used in E2E tests to simulate a real VNPay callback without needing
+ * the actual sandbox environment.
+ */
+export function buildVnpayCallbackData(
+  hashSecret: string,
+  opts: {
+    orderId: string;
+    amountVND: number;
+    responseCode?: string;
+    transactionNo?: string;
+  },
+): Record<string, string> {
+  const params: Record<string, string> = {
+    vnp_TxnRef: opts.orderId,
+    vnp_ResponseCode: opts.responseCode ?? '00',
+    vnp_Amount: (opts.amountVND * 100).toString(),
+    vnp_TransactionNo: opts.transactionNo ?? `VNP${Date.now()}`,
+    vnp_BankCode: 'NCB',
+    vnp_CardType: 'ATM',
+    vnp_OrderInfo: `E2E test payment ${opts.orderId}`,
+    vnp_PayDate: formatVnpayDate(new Date()),
+    vnp_TmnCode: process.env.VNPAY_TMN_CODE ?? 'TESTCODE',
+    vnp_TransactionStatus: opts.responseCode === '00' ? '00' : '02',
+  };
+
+  const sorted = sortObject(params);
+  const signData = new URLSearchParams(sorted).toString();
+  const hmac = crypto.createHmac('sha512', hashSecret);
+  const secureHash = hmac.update(Buffer.from(signData, 'utf-8')).digest('hex');
+
+  return { ...sorted, vnp_SecureHash: secureHash };
+}
+
+/**
+ * Generates a valid MoMo IPN callback payload with a correct HMAC-SHA256 signature.
+ */
+export function buildMomoCallbackData(
+  secretKey: string,
+  opts: {
+    orderId: string;
+    amount: number;
+    resultCode?: number;
+    transId?: string;
+  },
+): Record<string, string> {
+  const resultCode = opts.resultCode ?? 0;
+  const transId = opts.transId ?? `MOMO${Date.now()}`;
+  const requestId = crypto.randomUUID();
+  const extraData = '';
+  const message = resultCode === 0 ? 'Successful.' : 'Transaction failed.';
+  const orderInfo = `E2E test payment ${opts.orderId}`;
+  const orderType = 'momo_wallet';
+  const payType = 'qr';
+  const responseTime = Date.now().toString();
+  const partnerCode = process.env.MOMO_PARTNER_CODE ?? 'TESTPARTNER';
+  const accessKey = process.env.MOMO_ACCESS_KEY ?? 'TESTACCESSKEY';
+
+  const rawSignature = [
+    `accessKey=${accessKey}`,
+    `amount=${opts.amount}`,
+    `extraData=${extraData}`,
+    `message=${message}`,
+    `orderId=${opts.orderId}`,
+    `orderInfo=${orderInfo}`,
+    `orderType=${orderType}`,
+    `partnerCode=${partnerCode}`,
+    `payType=${payType}`,
+    `requestId=${requestId}`,
+    `responseTime=${responseTime}`,
+    `resultCode=${resultCode}`,
+    `transId=${transId}`,
+  ].join('&');
+
+  const signature = crypto
+    .createHmac('sha256', secretKey)
+    .update(rawSignature)
+    .digest('hex');
+
+  return {
+    orderId: opts.orderId,
+    amount: opts.amount.toString(),
+    extraData,
+    message,
+    orderInfo,
+    orderType,
+    partnerCode,
+    payType,
+    requestId,
+    responseTime,
+    resultCode: resultCode.toString(),
+    transId,
+    signature,
+  };
+}
+
+function formatVnpayDate(date: Date): string {
+  return date.toISOString().replace(/[-:T]/g, '').slice(0, 14);
+}
+
+function sortObject(obj: Record<string, string>): Record<string, string> {
+  const sorted: Record<string, string> = {};
+  for (const key of Object.keys(obj).sort()) {
+    sorted[key] = obj[key]!;
+  }
+  return sorted;
+}